Electric Meters

Electric Meters



An electric meter or electricity meter is a device used for measuring the amount of electrical energy supplied to a residence or company.

There are different types of electric meters available in the market, the most common of them being the (kilo) watt-hour meter or a joule meter. These meters generate invoice of the electricity after recording the measured values. The meter also records the time period for which the electricity was used.

Electric Meter

Unit of Measurement
These meters measure electricity in kilowatt-hour. A kilo watt hour can be explained as the amount of energy used by a load of one kilowatt over a period of one hour, or in other words 3,600,000 joules.

Types of Electric Meters
There are two types of prevalent electric meters being used all over the world. These meters operate by continuously measuring the instantaneous voltage (volts) and current (amperes) and multiplying the two for giving instantaneous electrical power (watts). The two types of electric meters are:

Solid State Meters
Solid state meters are modern electricity meters that display the power used on an LCD, and can be read automatically. These meters are gaining popularity the world over. These meters record useful information like:

* Maximum demand
* Power factor
* Reactive power used etc.

They meters can also have an electronic clock mechanism for computing a value, rather than an amount of electricity consumed. The pricing also varies according to the time of day, day of week, and seasonally.

Most of these meters use a current transformer for measuring current. This essentially means that the main current-carrying conductors need not pass through the meter itself. It can thus be located remotely from the main current-carrying conductors.


Electromechanical Meters
The most commonly used electricity meter is the electromechanical induction meter. This meter operates by counting the number of revolutions of an aluminium disc. This disc rotates at a speed proportional to the power. Thus the number of revolutions is proportional to the energy usage. The meter consumes a small amount of power, around 2 watts. An electromechanical induction meter's performance and accuracy can be affected by creep phenomenon. This occurs when the meter disc rotates continuously with potential applied and the load terminals open circuited.